The present invention relates to gas valves. In particular, the present invention is a solenoid controlled valve for controlling the flow of a compressed gaseous fuel (such as compressed natural gas) from a pressure vessel that utilizes the pressure vessel as a damage shield or protective "cocoon" for the solenoid valve.
With the increasing concern over air pollution caused by vehicles using internal combustion engines, and with the prospect of increasingly strict emission standards for urban vehicles with internal combustion engines, attention has been directed to use of alternate fuels such as compressed natural gas (CNG) as a fuel for vehicles such as cars, trucks and buses. The compressed natural gas is stored in a pressure vessel, and flow of the gas from the pressure vessel to the engine is controlled by a gas shut off valve.
A gas valve used in a vehicular application can be exposed to a wide variation of operating temperatures. For example, if the compressed natural gas tank is filled in the early morning when the outdoor temperature is relatively low, and the vehicle is parked outside on a blacktop asphalt surface during the heat of the day, the gas pressure within the pressure vessel can rise dramatically (from, for example, a nominal working pressure of about 3,600 psi to close to 5,000 psi). In the winter a vehicle may be fueled in frigid outdoor conditions and moved to a heated indoor garage. The gas valve must be capable of operating reliably over a wide temperature and pressure range.
Another major concern is the vulnerability of the gas valve to crash damage. If the vehicle is involved in an accident, the gas valve must not fail in a unsafe or catastrophic manner. Also the valve should automatically return to a normally closed position upon any indication of a problem such as interruption of electric power or activation of a safety device such as an air bag.